Why would a copy constructor have more than one parameter?

Question

$12.8/2 - \'A non-template constructor for class X is a copy constructor if its first parameter is of type X&, const X&, volatile X& or const

Answer 1

The BDE allocator [PDF Link] used this quirk. For example their array allocator looked like this:

template 
class bde::Array {
public:
    Array(bde::Allocator *allocator = 0);
    Array(const Array &rhs, bde::Allocator *allocator = 0);
};